API Versioning

Overview

API versioning is the strategy for identifying, releasing, supporting, evolving, and retiring distinct API contracts as interfaces or behavior change. API Versioning is the policy and mechanism for evolving contracts while controlling compatibility, support periods, migration, deprecation, and retirement. Versioning every small change creates fragmentation, while avoiding versions can produce silent breakage. Multiple versions also multiply security patches, tests, documentation, gateway rules, and support, and a version label cannot compensate for unclear compatibility policy. Strategies include path, header, media-type, query, date-based, or capability-based versions. The choice affects routing, documentation, caching, client generation, observability, and how consumers select or migrate between contracts. Providers should classify changes, prefer compatible evolution, version only at meaningful boundaries, and publish support and deprecation rules. Usage telemetry, contract comparison, overlap periods, migration tooling, and verified retirement keep the supported surface manageable. Emergency security fixes still need coordinated treatment across every supported version. Changes to API Versioning should be checked against older clients, stored payloads, enum growth, default behavior, and retry assumptions. Testing API Versioning should cover malformed input, denied access, rate limits, timeouts, duplicates, asynchronous completion, and version changes.

Data handled by API Versioning should use documented types, units, timestamp rules, nullable fields, and enum behavior to prevent silent interpretation errors.

The API Versioning contract should define identifiers, validation, authorization, status semantics, errors, limits, and version behavior at the same boundary.

For API Versioning, the application should preserve a correlation path from request construction through response, asynchronous completion, and final business state.

A successful transport result from API Versioning should not be interpreted beyond the exact API state documented by the provider.